add missing render function, fixes #4337

Closes #4337

Merge request studip/studip!3140

resources/vue/components/courseware/layouts/CoursewareCompanionBox.vue

 <script>
 export default {
     name: 'courseware-companion-box',
+    render(createElement) {
+        return null;
+    },
     props: {
         msgCompanion: String,
         mood: {

resources/vue/components/courseware/layouts/CoursewareCompanionOverlay.vue

@@ -3,6 +3,9 @@ import { mapActions, mapGetters } from 'vuex';
 
 export default {
     name: 'courseware-companion-overlay',
+    render(createElement) {
+        return null;
+    },
     computed: {
         ...mapGetters({
             showCompanion: 'showCompanionOverlay',